Ca2+-imaging in hundreds of CA1 pyramidal cells in a freely behaving mouse. A video showing a mouse exploring a circular arena (left panel) and the simultaneously acquired brain-imaging data of CA1 pyramidal cell Ca2+ activity, displayed as relative changes in fluorescence (deltaF/F) (right panel). 705 pyramidal cells were identified in the total data set and correspond to the neurons of Fig. 1b. The Ca2+-imaging frame rate was 20 Hz, but these data are shown down-sampled to 5 Hz to aid visualization of the Ca2+ transients. The video playback rate is sped up four-fold from how the events actually occurred.

Ca2+ Bursts Occur Spontaneously in Alert Resting Animals and Appear as a Radial Wave Expanding in Three Dimensions. A video clip taken from an 8 min recording acquired by three-dimensional (3D) two-photon microscopy in an awake, head-restrained mouse standing on the exercise ball, following injection of the cell membrane-permeant Ca2+-sensitive indicator OGB-1-AM into the cerebellar vermis. The video shows two examples of radially spreading bursts recorded in the cerebellar molecular layer across multiple optical planes at different depths below the pial surface. The planes shown range from 25-100 µm in depth spaced at 5 µm increments and were consecutively sampled at a rate of 49 ms per plane. The entire 3D stack was sampled at 1.1 Hz. Image data are displayed in a mosaic arrangement, with raw (left) and normalized (right) fluorescence signals. Normalized changes in fluorescence, deltaF(t)/F, were computed for each pixel as the difference between the instantaneous fluorescence, F(t), and the time-averaged fluorescence, F, divided by F. Elapsed time in seconds is shown in the upper right corner. Width of each individual image is 220 µm. Scale bar: 25 µm.

Ca2+ Flares are Triggered by Locomotion and Occur Across Areas Hundreds of Microns in Extent. This exemplary video taken from a 9.8 min recording in an awake head-restrained mouse shows Ca2+-activation in numerous Bergmann glial fibers across a 232 µm field of view before, during and after voluntary locomotor activity on an exercise ball. The time in seconds relative to movement onset is indicated in the upper right corner. Instantaneous running speed on the ball (in mm/s) as measured by the optical encoder is shown in the lower right corner. Fluorescence data were recorded in the cerebellar vermis by dual-color, two-photon microscopy following injection of the green fluorescent, cell membrane-permeant Ca2+-sensitive indicator OGB-1-AM (left) and topical application of the red fluorescent astrocyte marker SR101 (center). The right panel shows an overlay of the SR101 signals and normalized changes (deltaF(t)/F) in the OGB-1-AM signals, with the OGB-1-AM deltaF(t)/F signals represented in blue. Both primary glial fibers in the palisades highlighted by SR101 and the surrounding tissue areas participate in the Ca2+ flare.Virtually no motion artifacts are apparent, even when the mouse is running. The image acquisition rate was 20.35 frames per second, but to aid visualization of Ca2+-activation each frame in the movie shows an average of 10 consecutive frames. Scale bar, 25 µm.

Voltage trace (A) and phase plane trajectory
(B) of a rebound depolarization driven by a conditioned stimulus
in a model DCN neuron, following training with an intermediate interstimulus
int erval (ISI) of 90 ms. The stochastic arrival times of synaptic
inputs leads to variations in the voltage dynamics between the
20 traces shown, despite identical initial conditions at t =
-100 ms (red and blue traces). This ISI value leads to unreliable
retrieval of the stored memory. Noisy synaptic inputs lead some
phase plane trajectories (red dots) closer to the reliable retrieval
zone (warm colors in color map) and toward a higher level of
deinactivation of T-type Ca2+ channels, while other trajectories
are more distant from the reliable retrieval zone (blue dots).

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